Voltage limiting device



y 6, 1954 M. KERPCHAR 2,683,226

VOLTAGE LIMITING DEVICE Filed Sept. 50. 1950 ,2 FIG. 1

IN VEN TOR.

M/CHAEL KERPCHAR Patented July 6, 1954 VOLTAGE LIMITING DEVICE MichaelKerpchar, Clifton, N. J assignor to Bendix Aviation Corporation,Teterboro, N. J a corporation of Delaware Application September 30,1950, Serial No. 187,807

4 Claims. (Cl. 307149) The invention relates to voltage limitingdevices, and more particularly to a voltage limiting device whichproduces a sinusoidal output voltage.

The main object of the present invention is to limit the amplitude of asinusoidal voltage without distorting its wave form.

Another object is to provide a voltage limiting device which is simplein construction, requires When transformer I is excited, an alternatingvoltage dEe appears across secondary winding 5 and rectifier I9 passescurrent during the half cycle when end I5 of secondary winding 5 ispositive relative to center-tap 9, and rectifier 2| passes currentduring the half cycle when end I! of secondary Winding 5 is positiverelative to center-tap 9. A pulsating voltage 2E9, shown in Figure 2,appears across potentiometer I3 with relatively few parts, and iscompact in design. 10 side 23 positive relative to side I I.

Another object is to provide a device of the kind An adjustable tap 25on potentiometer I3 is described which can be used as a modulator.connected to one output terminal 26 and to one The inventioncontemplates a device having an input terminal 2! of an alternatingsignal source, input for receiving a signal and an output for such as anamplifier (not shown). As shown in producing a voltage corresponding tothe signal 1.; Figure 3, tap 25 of potentiometer I3 is positive but oflimited amplitude. An impedance is conrelative to side II and negativerelative to side nected between the input and output, and means 23 ofpotentiometer I3. Sides I I and 23 are conadapted to be energized by apulsating current nected through oppositely disposed rectifiers 30,provides for current flow through the impedance 3|, respectively, to theother output terminal 28 when the signal amplitude exceeds the limitingand through a, resistor 33 to the other input teramplitude so that avoltage drop occurs across minal 29 of the signal source. Resistor 33may the impedance to provide an output voltage corbe of relatively highvalue, preferably about responding to the signal but of limitedamplitude. 220,000 ohms.

The foregoing and other objects and advan- When a sinusoidal signal Esis impressed on tages of the invention will appear more fully 5terminals 21, 29, rectifier 38 passes current when hereinafter from aconsideration of the detailed terminal 29 is instantaneously negativerelative description which follows, taken together with to side II ofpotentiometer I3 and rectifier 3I the accompanying drawing, wherein oneembodipasses current when terminal 29 is instantanement of the inventionis illustrated. It is to be ously positive relative to side 23 ofpotentiometer expressly understood, however, that the drawing I 3. Suchcurrent flow occurs only when signal is for the purposes of illustrationand description E5 is instantaneously greater than voltage Ee. only, andis not to be construed as defining the The voltage Ee and the signalvoltage Es must be limits of the invention. in phase or 189 degrees outof phase with one In the drawing, another-that is, the nulls of thevoltage Ee and Figure 1 is a schematic wiring diagram showing signal Esmust occur simultaneously, otherwise a voltage limiter constructedaccording to the inthe output voltage E0 across terminals 26, 28 willvention; be distorted. The amplitude of voltage Ee deter- Figures 2 and3 show voltage curves for exciting mines the limit of the voltage E0.When the the voltage limiter shown in Figure l; and amplitude of signalEs is below the limiting value,

Figure 4a shows an input signal curve and cor- 0 then no current flowsin the circuit including responding output voltage curve of limitedamterminal 29, resistor 33, rectifiers 38, 3|, potentiplitude asdetermined by the exciting voltages of ometer i3 and terminal El, andthe output volt- Figures 2 and 3. age E0 is identical to the signal andappears Referring now to the drawing for a more deacross outputterminals 26, 2B. When the amtailed description of the novel voltagelimiter of 4.5 pli ude of the i nal ex eds the limi ing value, thepresent invention, the voltage limiter is as determined by voltage Ee,then current flows shown in Figure 1 as including a full waverectithrough the above circuit including rectifier 30 or fier with atransformer I having a primary windrectifier 3i as determined by thephase of the siging 3 excited by an alternating voltage and a, nal Es,and the output E0 is restricted to the limitcenter-tapped secondarywinding 5. The centering value Ee, as shown in Figur 4, because of thetap 9 of secondary Winding 5 is connected to one side II of apotentiometer I3 and opposite ends I5, I I of secondary winding 5 areconnected through rectifiers I9, 2| of any suitable kind to the otherside 23 of potentiometer I3.

voltage drop across resistor 33. in effect, short circuit the portion ofthe signal which exceeds the limiting value.

The device may be used as a modulator also by impressing the carriervoltage across termi- Rectifiers 30, 3 I,

3 nals 21, 29 and by impressing the modulating voltage across primarywinding 3 of transformer I. The modulated voltage will appear acrossoutput terminals 26, 2B.

The device provides a sinusoidal output of undistorted wave form and oflimited amplitude corresponding to a sinusoidal signal of varyingamplitude. The device is simple in construction, requires relatively fewparts, and is compact in design.

Although but one embodiment of the invention has been illustrated anddescribed in detail, it is to be expressly understood that the inventionis not limited thereto. Various changes can be made in the design andarrangement of the parts without departing from the spirit and scope ofthe invention as the same will now be understood by those skilled in theart.

What is claimed is:

1. In a device of the kind described, an input for receiving an A. C.signal, an output for producing a voltage corresponding to the signalbut of limited amplitude, an impedance connected in series with saidinput and said output, a potentiometer having a tap connected to oneside of said output, a full wave rectifier connected across saidpotentiometer and providing a pulsating voltage of the same frequency asthe signal, a pair of oppositely disposed rectifiers connected acrosssaid potentiometer and connected to said impedance and to the other sideof said output, said oppositely disposed rectifiers and saidpotentiometer being so arranged as to provide for current flow throughsaid impedance when the amplitude of the signal exceeds the amplitude ofthe pulsating voltage, whereby a voltage drop occurs across saidimpedance to provide an output voltage corresponding to the signal butof limited amplitude.

2. A voltage limiting device for an alternating current circuitincluding two lines, said device comprising a pair of parallel circuitsconnected across the lines, a rectifier and an impedance in series ineach circuit and the polarities of the rectifiers being opposite, analternating current source of the same frequency as the voltage to belimited, and a full-wave rectifier connecting said source to points inthe circuits between the rectifiers and impedances to oppose flow ofcurrent between the lines of the circuits,

3. A voltage limiting device having an input for receiving a signal ofreversible phase and an output connected thereto for producing a voltagecorresponding to the signal but of limited amplitude, a pair of parallelcircuits connected across said output and each circuit including arectifier and an impedance in series, the polarities of the rectifiersbeing opposite, an alternating current source of the same frequency asthe signal to be limited, a full-wave rectifier connecting said sourceto points in the circuits between the rectifiers and impedances tooppose flow of current through said circuits when the signal amplitudeis less than the limiting amplitude and to provide for current flowthrough said circuits when the signal amplitude exceeds the limitingamplitude.

4. A voltage limiting device having an input for receivin a signal ofreversible phase and an output for producing a voltage corresponding tothe signal but of limited amplitude, an impedance connected between saidinput and said output, a pair of parallel circuits connected across saidoutput and each circuit including a rectifier and an impedance inseries, the polarities of the rectifiers being opposite, an alternatingcurrent source of the same frequency as the signal, a full-waverectifier connecting said source to points in the circuits between therectifiers and impedances to oppose flow of current through saidcircuits when the signal amplitude is less than the limiting amplitudeand to provide for current flow through said circuits when the signalamplitude exceeds the limiting amplitude. whereby a voltage drop equalto the excess of the signal amplitude over the limiting amplitude occursacross said first impedance and a voltage corresponding to the signal,but of limited amplitude, appears at said output.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,144,995 Pulvari-Pulvermacher Jan. 24, 1939 2,438,518 PietyMar. 30, 1948 2,453,958 Anderson Nov. 16, 1948 2,455,732 Carter Dec. '7,1948 2,529,055 Smoot Nov. 7, 1950

